Every election is different, but they almost always come down to one question: What is the election about?

Some elections are about one or both of the candidates (personality, preparedness or accomplishments), while others are merely about “change.” Some are about the economy in general, or jobs or inflation in particular. A relative few are about national security or a military conflict.

Barack Obama's campaign made the 2012 election about Mitt Romney, which allowed the incumbent to win a second term even though his job approval numbers were low, voters were unhappy with the country’s direction and even some Democrats were disappointed with the president’s performance.

While issues tend to be less decisive than other concerns for swing voters (because they pay less attention to politics), the issue mix for 2016 can play a role in how all voters, swing and not swing, see their choices.

What issues will be decisive in 2016, and who has the advantage? Right now we can’t know the answer to those questions, but Democrats may have the initial edge.

While the country is divided on cultural issues, there is little doubt that progressives — and Democrats — are seen as more in tune with voters in general and swing voters in particular.

Conservatives have clearly lost the war on same-sex marriage and gay rights and while many Republicans are prepared to fight on, or try to redefine the struggle as about “religious liberty,” the die is pretty much cast.

Inclusiveness and opposition to discrimination have become revered political values for many, and the nation’s changing demographics are not likely to alter that.

Gallup’s May 6-10, 2015, survey found 60 percent of respondents said same-sex marriages should be “recognized by the law as valid, with the same rights as traditional marriages.” Only 37 percent of respondents disagreed. That is a significant shift from May 2010, when only 44 percent agreed.

The Pew Research Center’s polls show the same trend, with the greatest acceptance coming from the two youngest cohorts, millennials and Generation Xers, and the strongest opposition from voters age 70 and older, who will be leaving the electorate over the next couple of decades.

The attitudes of political independents now mirror those of Democrats on the issue — with almost two-thirds of each group supporting same-sex marriage — while only about one in three Republicans approve of those marriages.

Ironically, non-Hispanic blacks continue to be less enthusiastic about same-sex marriage than many other groups, but they are unlikely to support conservative (and therefore Republican) candidates because of other issues.

The most salient economic issue these days is not high taxes or the deficit or even over-regulation of business. It is economic inequality. That’s a decisive shift from the late 1970s and early 1980s, when taxes were a huge topic.

Progressives in the Democratic Party are scoring points on the left by raising the issue, with Massachusetts Sen. Elizabeth Warren, New York Mayor Bill DeBlasio and Vermont Sen. Bernard Sanders leading the charge over the past year.

But the issue’s salience is not only on the left.

Not everyone has the same take on the problem, but everyone seems to have an opinion. And that means that there is plenty of talk about the matter in the mainstream media (see here , here , here , here and here ).

To make things worse (for conservatives), even Pope Francis has left no doubt about his views on the subject, criticizing economic inequality and, in Bolivia recently , an “economy of exclusion and inequality.” While the pope’s views don’t change the discussion dramatically in this country, they give progressives another hook on which to hang their argument.

Republican strategists counter that Democrats’ focus on economic and income inequality is nothing new. One consultant with whom I spoke recently called it little more than a warmed over version of the “class warfare” argument Democratic strategists have been employing for years. Another GOP strategist agreed that economic concerns will be key during the 2016 race, but he too dismissed the current Democratic characterization as old hat and argued that Republicans have their own view of what is happening — a middle-class squeeze.

And, promised that veteran Republican, his party will use voters’ concerns about the economy to score points by arguing for more growth and blaming the White House for stagnant wages and a “yo-yo economy,” which seems unable to pick up any real momentum.

Given the salience of economic concerns with voters, both parties are likely to talk extensively about the economy, though using fundamentally different approaches and rhetoric. The party that wins this argument will have a leg up on an election victory.

Finally, there is foreign policy.

Democrats have plenty of problems here — Obama’s failures in the Middle East, his widely criticized negotiations with Iran and a general impression that he draws a line and then erases it — but they have one significant advantage: the public’s continued hesitance to use U.S. military power as a diplomatic weapon or on the battlefield.

While most GOP candidates and core voters yearn for a more aggressive, muscular foreign policy, with more defense spending, many voters appear nervous about another unsuccessful foreign intervention that risks American lives or costs American dollars.

Finally, immigration is something of a wild card. The country is divided on it, and how the issue plays out during the 2016 race depends on events (such as the recent shooting in California) and on the eventual Republican nominee. Obviously, Jeb Bush, Marco Rubio and even Rand Paul would discuss the issue differently than would Ted Cruz, Scott Walker or Donald Trump.

It’s important to remember the issue mix that is now developing for 2016 could change dramatically before next November, as events and news coverage alter public concerns and opinions. That’s another way of saying we don’t yet know what the next presidential election will be about.